His co-conspirators, Jose Ordonez Jr (47) and Julio Rivera (61), had previously also pleaded guilty to the same charge.
Mail fraud is defined in US law as any type of scheme involving fraud that crosses state lines and intentionally deprives others of property or communications through the mail. It carries a maximum penalty of 20 years in jail.
Sentencing will take place at a later date.
US attorney Greg Brooker said: “Antonio Buzaneli orchestrated a massive fraud scheme that victimised hundreds of individual investors around the globe, including in Minnesota.
“Many of these victims were elderly or vulnerable, and they invested their hard-earned retirement savings based on sophisticated lies about a complex investment Mr Buzaneli and his co-conspirators claimed to be making in Brazil.
“Instead, they used the investors’ money to fund their lifestyles, to travel first class around the world and to fund their other business ventures.”
Investors worldwide are understood to have lost more than $100m and it is highly unlikely that they will get their money back.
FBI acting special agent in charge Robert Bone said the “vast and sophisticated fraud scheme truly circled the globe, touching venues as near as St Louis Park, Minnesota and as far as Brazil, the United Kingdom and China”.
Providence opened offices and affiliates around the world; including in London, Hong Kong, Taipei, Shanghai, Singapore, Vancouver and Panama.
In 2011 and 2012, the company opened entities in Guernsey and Hong Kong, through which it raised around $85m from offshore investors.
“Buzaneli and his co-conspirators lured their victims with the promise of novel international investments and huge financial returns. In reality, they stole millions simply to fund their personal interests and maintain their fraudulent conspiracy,” Bone added.
The Providence fund operated from 2010 until June 2016, with the company filing for Chapter 7 bankruptcy protection in the US a month later.
Investors were promised returns of between 12-24% from investing money in a fund that bought company debt in Brazil at a discount. Providence claimed to make 48% returns.
Documents filed in court show that the company raised more than $64m from US investors by employing a network of brokers who sold promissory notes. Investors were assured that funds would be used “for the sole purpose” of making loans to a Brazilian subsidiary of Providence.
Instead, incoming client funds were used to pay “profits” to existing investors and broker commissions.
The Jersey Financial Services Commission (JFSC) shut down local IFA firm Lumiere Wealth, which was majority-owned by Providence, following an investigation into the sale of the funds to clients.